The major consideration in utilizing island flaps and free flaps of skin and subcutaneous tissue is tissue viability. Superoxide free radicals have been implicated in the etiology of cellular injury in various pathophysiological processes. The present proposal seeks to elucidate the role of superoxide free radicals in the tissue damage which occurs during ischemia and reperfusion. Allopurinol blockade of superoxide generation and scavengers of oxygen free radicals (superoxide dismutase, dimethyl sulfoxide, Alpha-tocopherol) will be investigated in terms of enhanced flap survival. The effect of hyperbaric oxygen on flap survival will be investigated to determine possible induction of antitoxidant enzymes. Additionally, the glutathione peroxidase system and reducing equivalents (NADH, NADPH, GSH) will be investigated. Fundamental knowledge concerning detoxification of free radicals will suggest therapeutic means for minimizing the effects of ischemia. Insights gained with respect to free flaps will prove valuable in the field of allotransplantation.